Gove , the former secretary of state for justice, has previously denied being one of the sources, saying in March: "I don't know how the Sun got all its information and I don't think it's really worth my adding anything to what's already been said."

Nick Clegg. REUTERS/Andrew Yates Speaking to the BBC's political editor Laura Kuenssberg in a documentary set to air on Monday evening, Clegg said: "Michael Gove obviously communicated it — well, I know he did, he gave this to The Sun"

He continued:

"I mean, the idea that the Queen of all people would even bother to give someone as insignificant as a 'here today, gone tomorrow' deputy prime minister a tongue lashing about Europe I just think is ... so preposterous, so it was not true ... I think it was very, very disrespectful of Michael Gove to have done that."

The documentary, "Brexit: Battle for Britain," will air on BBC Two at 9 p.m. (GMT) on Monday.